Monolithic integration of capacitive sensors using a double-side CMOS MEMS post process

• Published in: Journal of micromechanics and microengineering Vol. 19; no. 1; pp. 015023 - 015023 (9)
• Main Authors: Sun, Chih-Ming, Wang, Chuanwei, Tsai, Ming-Han, Hsieh, Hsieh-Shen, Fang, Weileun
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.01.2009; Institute of Physics
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Fluid dynamics; Fundamental areas of phenomenology (including applications); Instrumentation for fluid dynamics; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; Microelectronic fabrication (materials and surfaces technology); Micromechanical devices and systems; Physics; Precision engineering, watch making; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Accelerometers; Acceleration sensor; Pressure sensors; Semiconductor materials; Capacitive transducer; Bulk micromachining; System on a chip; Experimental study; Metal oxides; Proximity detector; Complementary MOS technology; Monolithic integrated circuits; Lateral etching; Distance measurement; Silicon; Surface layers; Microelectromechanical device; Sacrificial layer
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/19/1/015023

This study presents a novel double-side CMOS (complementary metal-oxide-semiconductor) post-process to monolithically integrate various capacitance-type CMOS MEMS sensors on a single chip. The CMOS post-process consists of three steps: (1) front-side bulk silicon etching, (2) backside bulk silicon etching and (3) sacrificial surface metal layers etching. Using a TSMC 2P4M CMOS process and the present double-side post-process this study has successfully integrated several types of capacitive transducers and their sensing circuits on a single chip. Monolithic integration of pressure sensors of different sensing ranges and sensitivities, three-axes accelerometers, and a pressure sensor and accelerometer are demonstrated. The measurement results of the pressure sensors show sensitivities ranging from 0.14 mV kPa-1 to 7.87 mV kPa-1. The three-axes accelerometers have a sensitivity of 3.9 mV G-1 in the in-plane direction and 0.9 mV G-1 in the out-of-plane direction; and the accelerated measurement ranges from 0.3 G to 6 G.